If you’re defaulting to visible for the spiders, but hidding the DIV via javascript for normal users, that seems similar to cloaking. Is it considered Black Hat SEO because the content is hidden? Isn’t it intentionally differing the appearance for the search engines?

I wouldn’t consider this Black Hat SEO because you are showing the copy on the page without having to go to another page or even refreshing the page. The copy in the include file is being displayed on the page it is intended for when a user chooses for the full copy to be displayed.

I dunno, I think this is one of those techniques you need to use sparingly for SEO purposes. It would only take one competitor dropping the dime on you to Google, saying, “Psst, check out all that hidden text these guys have.” The collapsable DIV is a useful design element, but I think SEOs need to be very careful using it.

I have done a quite exhaustive search into how using collapsible DIVs to ‘hide’ very long content (text or sometimes images) – and using a Read more or Plus and Minus type button to open/collapse the DIV if the user is interested – might affect search results with respect to the Hidden Text penalty, but can not find anything conclusive. Does anyone know the possible pitfalls of using this technique?

Specifically, this is for an Annual Report which has extremely long boring copy, and it is nicer to just show the intros and let the user decide if they want to read more. I have done it previously and the text that is hidden can be found on a SERP, so it is being indexed, but I wonder if there is a penalty to the rest of the site?

There are also a couple of ways to do it, using either pure javascript to declare the CSS ‘hidden’ attribute, or javascript and hard coded (external) CSS with a hidden attribute. Is there a safe way to do it?

My previous comment might have not gone through..
Just wanted to thank for the insightful article. I actually used collapsable “read more” a lot on couple of my websites and SE bots were always able to crawl. If they ranked for those keywords in that content was another issue…. to find them indexed, you would need to search the keywords in double quotations which users hardly do

I suspect that collapsed content is treated somewhat like content “below the fold” in Google’s page segmentation model. It’s indexed, it counts, it’s not penalized, but words in a boring annual report that’s collapsed dosn’t count as much as the first word in an h1 header at the top of your page.